Self-activating system and method for alerting when an object or a person is left unattended

ABSTRACT

A system and method uses a wireless tether comprising a transmitter and a receiver to alert a caregiver that an object or person has been left unattended. A detector senses the presence of the object, usually a child, located in a position such as a safety seat. The detector couples to the transmitter, which is located near the object. The transmitter transmits at least one wireless signal when the object is in the position. The receiver, which is remotely located from the transmitter, senses the at least one signal as long as the receiver is within a prescribed range of transmission. By performing a timing function, the receiver monitors the proximity of the caregiver, who maintains possession of the receiver, to the transmitter. The system communicates an alarm to the caregiver when the caregiver ventures outside the range of transmission without having removed the object/child from the position.

[0001] Pursuant to 35 U.S.C. §119, the benefit of priority fromprovisional application No. 60/329,692, with a filing date of Oct. 11,2001, is claimed for this non-provisional application.

ORIGIN OF THE INVENTION

[0002] The invention was made with Government support under contractNAS1-00135 awarded by NASA. The Government has certain rights in thisinvention.

BACKGROUND OF THE INVENTION

[0003] Field of the Invention

[0004] This invention relates to proximity sensing systems. Morespecifically, the invention is a self-activating system that alertssomeone when an object or a person is left unattended in a motor vehicleor other dangerous environment.

SUMMARY OF THE INVENTION

[0005] In accordance with the present invention, a self-activatingsystem is provided for alerting someone that an object or person hasbeen left unattended as is the case when a child is left restrained orunattended in a car seat. The system includes a detector for sensing thepresence and/or absence of the child in the car seat. Coupled to thedetector is a transmission means for automatically transmitting one of aplurality of unique wireless signals. For example, the plurality ofwireless signals may include a first signal when the child is in the carseat and a second signal when the child is removed from the car seat.Remotely located with respect to the transmission means is a receivingmeans capable of sensing the plurality of wireless signals, includingthe first signal and the second signal. The receiving means is possessedby the parent or other responsible caregiver who is also generally thedriver of the vehicle in which the car seat is located. The receivingmeans is programmed to carry out a plurality of timing functionsincluding a first timing function and a second timing function. Thefirst timing function is enabled when the first signal is initiallysensed. Once enabled, the first timing function times to a firstinterval or intervening period of time. At the completion of each firstinterval, the receiving means can implement a variety of actions.Specifically, the receiving means (i) continues the first timingfunction if the first signal is sensed indicating that the receiver isstill in proximity to the child in the car seat; (ii) disables the firsttiming function if the second signal is sensed indicating that the childhas been removed from the car seat; or (iii) enables the second timingfunction if neither of the first signal nor the second signal is sensed.The second timing function indicates that the responsible caregiverpossessing the receiving means has ventured outside the range of thetransmission means while the child is still located in the car seat. Ifenabled, the second timing function times to a second interval having afirst time and a later second time. The receiving means issues a firstalarm signal at the first time if neither the first nor second signal issensed. However, the receiving means discontinues the first alarm signalif the first signal is sensed during the second interval indicating thatthe responsible caregiver (possessing the receiving means) has returnedwithin the range of the transmission means while the child is stilllocated in the car seat. Further, the receiving means issues a secondalarm signal if the first signal is not sensed during the secondinterval. The second alarm signal is allowed to continue after thesecond time until the second signal is sensed. That is, the second alarmsignal continues until the responsible caregiver (possessing thereceiving means) has returned to the vicinity of the transmission andthe child is removed from the car seat.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a schematic block diagram of a self-activating systemfor alerting a caregiver that a child has been left unattended in avehicle in accordance with an embodiment of the present invention;

[0007]FIG. 2 is a perspective view of a child safety seat with apressure switch attached to its seat and back areas to serve as adetector for the presence of a child in accordance with an embodiment ofthe present invention;

[0008]FIG. 3 is a flow diagram depicting the basic steps for thetransmission portion of the system when two unique wireless signals areused in accordance with one embodiment of the present invention;

[0009]FIG. 4 is a flow diagram depicting the basic steps for thereception portion of the system when two unique wireless signals areused in accordance with one embodiment of the present invention;

[0010]FIG. 5 is a flow diagram depicting the basic steps for thetransmission portion of the system when three unique wireless signalsare used in accordance with another embodiment of the present invention;

[0011]FIG. 6 is a portion of the flow diagram depicting the additionalsteps for the reception portion of the system when three unique wirelesssignals are used in accordance with another embodiment of the presentinvention;

[0012]FIG. 7A is a schematic block diagram of a self-activating systemfor alerting a caregiver that at least one child has been leftunattended in at least one child safety seat in accordance with anotherembodiment of the present invention;

[0013]FIG. 7B is a schematic block diagram of a self-activating system,having two detectors, for alerting a caregiver that at least one childhas been left unattended in at least one child safety seat in accordancewith another embodiment of the present invention;

[0014]FIG. 8 is a flow diagram depicting the basic steps carried out bythe transmission portion of a system when two child safety seats arebeing monitored; and

[0015] FIGS. 9A-9C are flow diagrams depicting the basic steps carriedout by the reception portion of a system when two child safety seats arebeing monitored.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Referring now to the drawings, and more particularly to FIG. 1, aschematic block diagram of a self-activating system of the presentinvention that provides an alerting or alarm signal when an object orperson has been left unattended is shown and referenced generally bynumeral 10. By way of illustrative example, the present invention willbe explained as a system for alerting a parent or other caregiver that achild has been left unattended in a safety seat within a vehicle.However, as will be apparent from the following, it is to be understoodthat the present invention can be used to provide an alarm signal whenany object, or a restrained or otherwise immobilized individual, hasbeen left unattended in any position.

[0017] System 10 includes a transmission portion 20 and a receptionportion 30. Transmission portion 20 remains at a position close to wherethe individual (or object) 100 has been left. In terms of theillustrated example, individual 100 is a child positioned and restrainedin a safety seat 102 as shown in FIG. 2. Accordingly, transmissionportion 20 is located on or near the seat 102. Reception portion 30 ispossessed by someone responsible for individual 100. Again, in terms ofthe illustrative example, reception portion 30 is maintained by theparent or caregiver 150 having responsibility for individual 100.Typically, the caregiver 150 would be the driver of the vehicle thatindividual 100 is in. Because it is important for the caregiver 150 tomaintain possession of reception portion 30, reception portion 30 may beattached to or kept with the motor vehicle's key, such as, for example,a key ring. This arrangement will work in the vast majority ofsituations as it is presumed that the motor vehicle key will be retainedat all relevant times by caregiver 150 who is responsible for individual100.

[0018] Transmitter portion 20 includes a detector 22 for monitoring orsensing the presence or absence of individual 100, a controller 24coupled to detector 22 for “reading” the state of detector 22 andsending an activating signal, and a transmitter 26 coupled to andcontrolled by controller 24 for transmitting a plurality of uniquewireless signals 28. Transmission portion 20 will typically have its ownreplaceable power source 21 such as a battery to power appropriatecomponents in transmission portion 20. Transmission portion 20 mayinclude a device that can provide a caregiver with an indication thattransmitter portion 20 is working and that power source 21 hassufficient power capability. For example, transmitter portion 20 caninclude an audio device 27 to provide an audible indication each timedetector 22 initially senses the presence of individual 100 and whenindividual 100 is no longer sensed by detector 22. Audio device 27 couldalso be used to provide an audible alarm when it is time to replacepower source 21.

[0019] Detector 22 comprises any type of device that senses the presenceand absence of individual 100. For instance, the detector 22 maycomprise a mechanical switch, an optical detector, a heat detector, asonar detector, a motion detector, or a weight or pressure detector. Forpurposes of the illustrated example, FIG. 2 shows that detector 22 maybe realized by a tape pressure switch 220 that attaches to the safetyseat 102 (the padded cover and restraining belts/straps of which are notshown for clarity of illustration) along both its seat support area 102Aand its back support area 102B. Tape pressure switch 220 is normally anopen switch that closes when there is pressure against any portionthereof. Such tape pressure switches are well known in the art. In termsof placement, tape pressure switch 220 could be serpentined across seatarea 102A and back area 102B. The advantage of having switch 220 spanboth seat area 102A and back area 102B is that switch 220 will close andremain closed even if the individual 100 becomes fidgety. Although onlyone switch 220 is shown, more than one pressure switch could be usedwithout departing from the scope of the invention.

[0020] Controller 24 is a programmable microprocessor-based device thatinstitutes its processing steps predicated on the state of detector 22,i.e., switch 220 is open indicating no child is in the car seat orswitch 220 is closed indicating that a child is in the car seat.Controller 24 processes the state of detector 22 and issues controlsignals to transmitter 26. The control signals activate and/ordeactivate transmitter 26 and control the type of wireless signal 28that will be transmitted.

[0021] Transmitter 26 is any omnidirectional wireless transmitter thatcan output a plurality of unique wireless signals 28 such as radiofrequency (RF) signals. The particular unique wireless signal is, at anygiven time, dictated by controller 24. The strength of wireless signals28 should be such that they are only detectable (by reception portion30) over a predetermined range. For the illustrative example, thepredetermined range of transmission is on the order of approximately10-20 feet for reasons that will be explained further below. Theuniqueness of wireless signals 28 can be achieved by using differentfrequencies for each signal, or otherwise uniquely encoding (e.g.,frequency shift keying, modulation, pulse width, bit phase shift keying,manchester coding, etc.) each signal. Such encoding and transmittingtechniques are well known in the art of wireless tethers and include thetechniques and system disclosed in U.S. Pat. No. 6,075,443, which ishereby incorporated by reference. Alternatively, wireless signals whichare not unique or encoded may also be used.

[0022] Reception portion 30 includes a receiver 32 for receivingtransmission of wireless signals 28 provided receiver 32 is within theafore-mentioned predetermined range of transmitter 26, a controller 34coupled to receiver 32, and one or more alerting device(s) 36 coupled tocontroller 34. Reception portion 30 will typically have its ownreplaceable power source 31 such as a battery to power each appropriatecomponent in reception portion 30. The reception portion 30 may alsoinclude an alarm reset to allow the caregiver to reset the unit. Thisreset enables one caregiver to reset their alarm if another caregiver(having his own reception portion) remains with the child.

[0023] Alerting device(s) 36 are activated and/or deactivated bycontroller 34 and can include one or more of an audio producing devicesuch as a voice generator or a beeper, a visual device such as flashinglights, or a tactile device such as a vibrator, etc. In the illustrativeexample, alerting device(s) 36 would, at a minimum, include an audioproducing device.

[0024] Controller 34 is a programmable microprocessor-based device thatinstitutes its processing steps predicated on the unique nature ofwireless signal 28 received by receiver 32. Receiver 32/controller 34use such receiving and decoding techniques as are well known in the artof wireless tethers. Such techniques include the system disclosed in theU.S. Pat. No. 6,075,443, which is hereby incorporated by reference.Controller 34 then issues control signals to alerting device(s) 36 toactivate or deactivate the same.

[0025] By way of non-limiting illustrative examples, the presentinvention will be explained using two and three unique wireless signalstransmitted by transmitter 26. Processing based on the use of twosignals will first be explained with the aid of FIGS. 3 and 4 where FIG.3 depicts the operation of transmission portion 20 and FIG. 4 depictsthe operation of reception portion 30.

[0026] Referring first to FIG. 3, controller 24 continuously orperiodically (i.e., to save battery power) polls the state of detector22 at step 200. Specifically, the presence or absence of a child in thecar seat is determined. If the child is present, controller 24 instructstransmitter 26 to transmit an ALIVE signal. This instruction can beissued continuously or periodically (i.e., again to save battery power)at step 202. Once the ALIVE signal has been transmitted, detector 22 isagain checked at step 204. If the child is still in the car seat, theALIVE signal is continuously or periodically transmitted again. If,however, the child has been removed from the car seat, controller 24instructs transmitter 26 to transmit a DISABLE signal at step 206 andtransmission control returns to step 200.

[0027] Referring now to FIG. 4, receiver 32/controller 34 work togethercontinuously or periodically to check for an ALIVE signal at step 300.If no ALIVE signal is detected, the main processing steps of receptionportion 30 remain inactive. Initial detection of the ALIVE signal (i.e.,child placed in the safety seat 102) enables a first timing sequencehaving a first interval of time at step 302. At the conclusion of thetiming sequence (e.g., on the order of 10-60 seconds) receiver32/controller 34 operate to check for an ALIVE signal at step 304 andDISABLE signal at step 306. Detection of an ALIVE signal (indicatingthat the child is still in the seat 102) causes the timing sequence instep 302 to repeat itself. This repeated sequence essentially means thatthe child is in the car seat and reception portion 30 (in possession ofthe caregiver 150) is within the predetermined range (e.g., 10-20 feet)of the car seat. On the other hand, detection of a DISABLE signal(indicating that the child is now out of the car seat) returns thecontroller 34 to step 300. If neither the ALIVE or DISABLE signal isdetected at the completion of the step 302 timing sequence, a secondtiming sequence is initiated at step 308. This second timing sequenceessentially means that the child is in the car seat, but that receptionportion 30 is no longer in range to receive the ALIVE signal. Assumingthat the caregiver 150 has maintained possession of the receptionportion 30, this circumstance also indicates that the caregiver 150 isno longer in the vicinity of the safety seat. Therefore, the controller34 is passed on to step 308, which is the beginning of the second timingsequence.

[0028] Step 308 times to a first time (TIME 1) and then to a latersecond time (TIME 2). For example, TIME 1 could occur at 1 minute andTIME 2 could occur at 2 minutes. At TIME 1, if either the ALIVE orDISABLE signals are detected at steps 310 and 312, respectively, thecontroller 34 returns to steps 302 or 300, respectively. However, ifneither of these signals is detected (indicating that reception portion30 remains beyond the predetermined transmission range capability oftransmission portion 20), a first alarm signal is issued at step 314. Interms of system 10, controller 34 issues a control signal to alertingdevice(s) 36 to produce a first alarm in correspondence with the firstalarm signal. The first alarm serves as a pre-warning to the possessorof reception portion 30 that he (the caregiver 150) is out of range oftransmission portion 20 during the time that reception portion 30 isactivated. That is, the first alarm indicates that the possessor ofreception portion 30 has left the vicinity of the vehicle while thechild has been left in the car seat. The pre-warning could, for example,be a series of audible beeps, blinking lights, or vibrations issued byalerting device(s) 36. Alternately, alerting device 36 may comprise avoice generator that generates a voice message such as “RETURN TO CAR!”or “REMOVE CHILD FROM SEAT!”

[0029] As second timing sequence step 308 continues timing to TIME 2,the first alarm signal is issued while reception portion 30 continuouslyor periodically looks for an ALIVE or DISABLE signal at steps 316 and318, respectively. Detection of a respective one of these signalsindicates that the possessor of reception portion 30 is again within thepredetermined range of transmission portion 20, i.e., the caregiver 150has returned to the vicinity of the vehicle. When this event occurs, thefirst alarm signal is discontinued as the controller 34 is returned tothe appropriate one of steps 302 or 300. However, if neither of theALIVE or DISABLE signals is detected (again indicating that receptionportion 30 is beyond the predetermined transmission range oftransmission portion 20), a second alarm signal is issued at TIME 2 atstep 320. In terms of system 10, controller 34 issues a control signalto alerting device(s) 36 to produce a second alarm in correspondencewith the second alarm signal. The second alarm could be the same ordifferent than the first alarm. The second alarm continues until aDISABLE signal is detected at step 322, at which point the second alarmsignal is stopped at step 324 and control is returned to step 300.Essentially, processing step 320 is only executed if the possessor ofreception portion 30 did not return to the vicinity of the vehicle inresponse to the (pre-warning) first alarm signal.

[0030] As mentioned above, the present invention can also be based onthe use of three unique wireless signals where the addition of a briefENABLE signal is used in conjunction with the above-described ALIVE andDISABLE signals. The processing steps implementing the transmissionportion of this embodiment are depicted in FIG. 5 and the processingsteps implementing the reception portion of this embodiment are depictedin FIG. 6. Processing steps that remain unchanged are tagged with thesame reference numerals and will not be described further.

[0031] In FIG. 5, processing steps 201 are carried out after theabove-described step 200. Specifically, when a child is first detectedin the car seat, an ENABLE signal (e.g., a brief pulse) is transmittedat step 201A. Then, periodically or continuously, the car seat'sdetector is again polled at step 201B. Presence of the child causestransmission of the ALIVE signal at step 202 whereas absence of thechild causes transmission of the DISABLE signal at step 206 with controlthen being returned to step 200.

[0032] The inclusion of processing steps 201 at transmission portion 20results in the addition of steps 298 and 299 in reception portion 30 asillustrated in FIG. 6. Specifically, reception portion 30 continuouslyor periodically looks for an ENABLE signal at step 298. If present, anaudio output at transmission portion 20 can be generated by audio device27 at step 299. Control is then passed to step 302 and processingcontinues as described previously in FIG. 4. However, recognizing that achild can be placed in the car seat before the reception portion 30comes within range (e.g., reception portion 30 is in the house or withthe other parent when the child is placed in the car seat), lack ofdetection of the ENABLE signal at step 298 transfers the controller 34to step 300 and processing continues as described previously.

[0033] The present invention can also be based on the use of one uniquewireless signal wherein only the above-described ALIVE signal istransmitted. The processing steps implementing the transmission portionof such a single-signal system would be similar to the processing stepsdepicted in FIG. 3, but the step of transmitting a DISABLE signal wouldbe eliminated. In the same way, the processing steps implementing thereception portion of such a single-signal system would be similar to theprocessing steps depicted in FIG. 4, but the steps of checking for aDISABLE signal would be eliminated.

[0034] Operation of the system enables a self-activating method foralerting a caregiver that a child has been left unattended in a childsafety seat. The system continuously or periodically monitors the safetyseat and automatically (by itself) activates once the child is placed inthe seat. Then, as long as the caregiver 150 is in possession of thereception portion 30 and remains in close proximity to the transmitterwhich is located at or near the seat, no alarm is sounded. In otherwords, the caregiver 150 is wirelessly tethered by the system 10 by theact of maintaining the reception portion 30 in the vicinity of caregiver150. In one embodiment, once the child is placed in the seat and thesystem is activated, the caregiver 150 can only leave the vicinity (ofthe child safety seat) for a brief period of time before a pre-warningalarm is issued to encourage the caregiver to return immediately to thevehicle. If the caregiver does not respond quickly enough, a secondalarm is issued and will continue until the caregiver (in possession ofthe reception portion of the system) returns and the child is removedfrom the seat.

[0035] Alternatively, the function of communicating an alarm to thecaregiver may be performed with a system 10 that communicates only onealarm to the caregiver (without providing a pre-warning alarm as justdescribed) once the caregiver is beyond a predetermined distance fromthe child. With such a system, the single alarm may be deactivated inthe same manner described earlier for either the first or second alarm.In other words, the single alarm may be deactivated by having thecaregiver 150 return within the range of transmission of the transmitter26. In another embodiment, the single alarm may be deactivated only byhaving the child removed from the safety seat.

[0036] The present invention can be constructed with inexpensive,commercially-available components that are both small in size and of lowpower consumption. A child safety seat and vehicle need not befunctionally or materially altered to install the system of the presentinvention. Thus, the present invention may be installed with anyexisting or new safety seat and/or vehicle.

[0037] Numerous variations and modifications will be readily apparent tothose skilled in the art in light of the above teachings. For example,additional audio tones or voice messages can be used at both thetransmission and reception portions to indicate that the system has beenactivated, periodically indicate that the system is still activated, orindicate that the system has been deactivated. In one embodiment, thealerting device 36 may include a voice generator (not shown) thatgenerates such voice messages as “ACTIVATED,” “WORKING,” and“DEACTIVATED.” Still other audible alarms or voice messages can beprovided to indicate that respective power sources 21 and 31 need to bereplaced. In another embodiment, a watch dog circuit may be combinedwith a wake-up circuit to turn off the alarm of the reception portionafter sounding for a sufficiently long period of time, thereby avoidinga substantial draining of a power source such as a replaceable battery.

[0038] Similarly, while the illustrated example of FIG. 1 and thepreceding detailed description has discussed a system 10 and a methodfor “a caregiver,” “a child,” and “a safety seat,” it should beunderstood that the system and method may also encompass a plurality ofchildren that are each located in a different safety seat within thesame vehicle or a plurality of caregivers. Likewise, while the system 10has been described as having “a detector,” “a transmission portion,” or“a reception portion,” the specification and appended claims are to beunderstood as encompassing systems and methods comprising more than onedetector, one transmission portion, or one reception portion. Forexample, if more than one reception portion is used (i.e. two caregiversare responsible for one child), each reception portion may include analarm reset to enable one caregiver to reset their unit while the othercaregiver remains with the child.

[0039] Examples of such systems and methods are illustrated in FIGS. 7Aand 7B. Both system 10A of FIG. 7A and system 10B of FIG. 7B encompass ascenario wherein one caregiver 150 is responsible for two individuals(children) each positioned in a different safety seat. Components ofsystem 10A and system 10B that remain substantially unchanged from theprevious description are tagged with similar reference numerals. Forinstance, reception portion 30A comprises similar components andoperates in a similar manner to reception portion 30.

[0040] System 10A, as shown in FIG. 7A, comprises two transmissionportions 20A and 20A′ including two detectors 22A and 22A′, twotransmission controllers 24A and 24A′, and two transmitters 26A and26A′, respectively. Transmitter 26A sends a plurality of wirelesssignals 28A, whereas transmitter 26A′ sends a second plurality ofwireless signals 28A′. Reception portion 30A includes a receiver 32A, acontroller 34A, and an alerting device 36A.

[0041] Referring now to FIG. 7B, system 10B comprises two detectors 22Band 22B′, one transmitter controller 24B, and one transmitter 26B.Transmitter 26B transmits a plurality of wireless signals 28B. Receptionportion 30B includes a receiver 32B, a controller 34B, and an alertingdevice 36B.

[0042] The critical difference between the system 10 previouslydescribed and the two alternative embodiments 10A and 10B is that thealternative embodiments transmit a set of signals for each safety seatbeing monitored, thereby requiring a slightly different set ofsignal-processing techniques than the techniques presented previously inFIGS. 3 and 4. This different set of signal-processing techniques isnecessary because system 10A and system 10B should activate when eitherone or both seats are occupied and should deactivate only when bothseats are unoccupied.

[0043] Accordingly, transmission portions 20A, 20A′, and 20B differslightly from the previously described transmission portion 20. First,transmitter controllers 24A, 24A′, and 24B each send an ALIVE signal totransmitters 26A, 26A′, and 26B, respectively, when either one or bothsafety seats are occupied. Controllers 24A, 24A′, and 24B also send aDISABLE signal to transmitters 26A, 26A′, and 26B, respectively, when aseat is unoccupied. Likewise, reception portions 30A and 30B differ fromthe previously described reception portion 30 in that receivercontrollers 34A and 34B send a deactivating signal to the alertingdevice 36A and 36B, respectively, only when both monitored safety seatsare unoccupied.

[0044] Examples of the signal processing performed by systems 10A and10B, based on the use of four different signals, are shown in FIGS. 8and 9A-9C. By way of non-limiting illustrative examples, the system 10Awill be explained using two unique wireless signals transmitted bytransmitter 26A and two unique or coded wireless signals transmitted bytransmitter 26A′. Similarly, system 10B will be explained using fourunique or coded wireless signals transmitted by transmitter 26B. Inthese examples, both systems use a total of four different signals, butthe system may use additional signals, such as the third ENABLE signalpreviously described in FIGS. 5 and 6, and still be within the scope ofthe invention. FIG. 8 depicts the operation of transmission portions20A, 20A′, and 20B, and FIGS. 9A-9C depict the operation of receptionportions 30A and 30B.

[0045] Referring first to FIG. 8, controllers 24A and 24A′ continuouslyor periodically (i.e., to save battery power) poll the state ofdetectors 22A and 22A′, respectively, at step 199A. Similarly,controller 24B continuously or periodically (i.e., to save batterypower) polls the state of detectors 22B and 22B′, respectively, at step199A. Specifically, the controllers determine the presence or absence ofchildren in the two safety seats. If a child is present in the firstsafety seat, then controllers 24A and 24B instruct transmitters 26A and26B, respectively, to transmit an ALIVE #1 signal. This instruction canbe issued continuously or periodically (i.e., again to save batterypower) at step 202A. If, on the other hand, the first safety seat isunoccupied, the controllers 24A and 24B instruct transmitters 26A and26B, respectively, to transmit a DISABLE #1 signal at step 206A. Thisinstruction can also be issued continuously or periodically. Once theALIVE #1 or DISABLE #1 signal has been transmitted, detectors 22A′ and22B′ are checked at step 200B. If a child is present in the secondsafety seat, then controllers 24A′ and 24B instruct the transmitters26A′ and 26B, respectively, to transmit, continuously or periodically,an ALIVE #2 signal at step 202B. If, on the other hand, the secondsafety seat is unoccupied, the controllers 24A′ and 24B instructtransmitters 26A′ and 26B, respectively, to transmit a DISABLE #2 signalat step 206B. Accordingly, a DISABLE signal is transmitted whenever asafety seat remains unoccupied or when a child has been removed from thesafety seat.

[0046] Referring now to FIGS. 9A-9C, receivers 32A and 32B work togethercontinuously or periodically with controllers 34A and 34B, respectively,to check for an ALIVE #1 and ALIVE #2 signal beginning at step 297 andproceeding as indicated at steps 301A and 301B. If neither an ALIVE #1signal at step 301A nor an ALIVE #2 signal at step 301B are detected,the main signal processing steps of reception portions 30A or 30B remaininactive. The main signal processing steps remain inactive becauseeither the receiver is outside the transmission range of the transmitteror both seats are unoccupied. Both of these scenarios presume thecaregiver (who has possession of the receiver) has not begun using thesystem because he or she is not in the vicinity of the transmitter tobegin activating the system or because a child is not occupying eitherseat.

[0047] Initial detection of an ALIVE #1 signal (i.e., child placed inthe first safety seat) at step 301A or of an ALIVE #2 signal (i.e.,child placed in the second safety seat) at step 301B enables a firsttiming sequence at step 302A. At the conclusion of the first timingsequence (e.g., on the order of 10-60 seconds), receivers 32A and 32Band controllers 34A and 34B operate to check for a DISABLE #1 signal atstep 304A and a DISABLE #2 signal at step 304B. Detection of both aDISABLE #1 and a DISABLE #2 signal (indicating that both seats are nowunoccupied) causes the first timing sequence to exit and return to thefirst act of monitoring at step 297.

[0048] If the receivers/controllers do not detect a DISABLE #1 signal atstep 304A, then they next check for an ALIVE #1 signal at step 306A. Ifan ALIVE #1 signal is detected, then the first timing sequence repeatsitself as the system reverts back to step 302A. This repeated sequenceessentially means that the child is in the first safety seat andreception portion 30A or 30B (in possession of the caregiver) is withinthe predetermined range (e.g., 10-20 feet) of the safety seat. On theother hand, if an ALIVE #1 signal is not detected at the completion ofthe first timing sequence at step 306A, a second timing sequence isinitiated at step 308A. This second timing sequence essentially meansthat the child is in the first safety seat, but that reception portion30A or 30B is no longer in range to receive the ALIVE #1 signal.Assuming that the caregiver has maintained possession of the receptionportion 30A or 30B, this circumstance also indicates that the caregiveris no longer in the vicinity of the first seat. Therefore, thecontroller 34A or 34B is passed on to the second timing sequence at step308A.

[0049] If the receivers 32A, 32B and controllers 34A, 34B detect aDISABLE #1 signal at step 304A but do not detect a DISABLE #2 at step304B, then they next check for an ALIVE #2 signal at step 306B. If anALIVE #2 signal is detected, then the first timing sequence repeatsitself as the system reverts back to step 302A. This repeated firsttiming sequence essentially means that a child is in the second safetyseat and reception portion 30A or 30B (in possession of the caregiver)is within the predetermined range (e.g., 10-20 feet) of the safety seat.On the other hand, if an ALIVE #2 signal is not detected at thecompletion of the first timing sequence at step 306B, the second timingsequence is initiated at step 308A. Here, this second timing sequenceessentially means that a child is in the second safety seat, but thatreception portion 30A or 30B is no longer in range to receive the ALIVE#2 signal. Assuming that the caregiver has maintained possession of thereception portion 30A or 30B, this circumstance also indicates that thecaregiver is no longer in the vicinity of the second seat. Therefore,the controller 34A or 34B is passed on to the second timing sequence atstep 308A.

[0050] Referring now to FIG. 9B, step 308A times to a first time (TIME1A) and then to a later second time (TIME 2A). For example, TIME 1Acould occur at 30 seconds and TIME 2A could occur at 1 minute. At TIME1A, if both the DISABLE #1 signal and the DISABLE #2 signal are detectedat steps 310A and 310B, respectively, then the controller 34A or 34Bexits the second timing sequence and returns to step 297. This exit ofthe second timing sequence essentially means that the caregiver hasreturned to the vicinity of the two safety seats and both seats are nowunoccupied. If the receivers/controllers do not detect a DISABLE #1signal at step 310A, then they next check for an ALIVE #1 signal at step312A. If an ALIVE #1 signal is detected, then the second timing sequenceis exited and the system reverts back to step 302A. This exit of thesecond timing sequence essentially means that the caregiver has returnedto the vicinity of the first safety seat while the seat remainsoccupied.

[0051] If an ALIVE #1 signal is not detected at step 312A, a first alarmsignal is issued at step 314A. In terms of system 10A and 10B,controller 34A and 34B issue a control signal to alerting device(s) 36Aand 36B, respectively, to produce a first alarm in correspondence withthe first alarm signal. The first alarm serves as a pre-warning to thepossessor of reception portion 30A or 30B that he or she is out of rangeof transmission portion 20A or 20B, respectively, during the time thatreception portion 30A or 30B is activated. That is, the first alarmindicates that the possessor of reception portion 30A or 30B has leftthe vicinity of the vehicle and at least one child has been left in atleast one safety seat. The pre-warning could, for example, be a seriesof audible beeps issued by alerting device(s) 36A or 36B.

[0052] If the receivers 32A, 32B and controllers 34A, 34B detect aDISABLE #1 signal at step 310A but do not detect a DISABLE #2 at step310B, then they next check for an ALIVE #2 signal at step 312B. If anALIVE #2 signal is detected, then the second timing sequence is exitedand the system reverts back to step 302A. This exit of the second timingsequence essentially means that the caregiver has returned to thevicinity of the second safety seat while the seat remains occupied. Ifan ALIVE #2 signal is not detected at step 312B, a first alarm signal isissued at step 314A. Again, the first alarm serves as a pre-warning tothe possessor of reception portion 30A or 30B that he or she is out ofrange of transmission portion 20A or 20B, respectively, during the timethat reception portion 30A or 30B is activated. That is, the first alarmindicates that the possessor of reception portion 30A or 30B has leftthe vicinity of the vehicle and at least one child has been left in atleast one safety seat.

[0053] After the first alarm signal is issued, the second timingsequence progresses to TIME 2A at step 316A. Reception portion 30A or30B now continuously or periodically look for a DISABLE #1 signal atstep 316A and, if received, a DISABLE #2 signal at step 316B. Detectionof both of these signals indicates that the caregiver has returned tothe vicinity of the two safety seats and both seats are now unoccupied.The respective controller exits the second timing sequence and proceedsto step 324A, where it stops the first alarm signal and then returns tostep 297.

[0054] If the receivers/controllers do not detect a DISABLE #1 signal atstep 316A, then they next check for an ALIVE #1 signal at step 318A. Ifan ALIVE #1 signal is detected, then the second timing sequence isexited. The controller (34A or 34B) stops the first alarm signal and thesystem reverts back to step 302A. This exit of the second timingsequence essentially means that the caregiver has returned to thevicinity of the first safety seat while the seat remains occupied. If anALIVE #1 signal is not detected at step 318A, a second alarm signal isissued at step 320A. In terms of system 10A and 10B, controller 34A and34B issue a control signal to alerting device(s) 36A and 36B,respectively, to produce a second alarm in correspondence with thesecond alarm signal.

[0055] If the receivers/controllers do not receive a DISABLE #2 signalat step 316B, then they next check for an ALIVE #2 signal at step 318B.If an ALIVE #2 signal is detected, then the second timing sequence isexited. The controller (34A or 34B) stops the first alarm signal and thesystem reverts back to step 302A. This exit of the second timingsequence essentially means that the caregiver has returned to thevicinity of the second safety seat while the seat remains occupied. Ifan ALIVE #2 signal is not detected at step 318B, a second alarm signalis issued at step 320B. In terms of system 10A and 10B, controller 34Aand 34B issue a control signal to alerting device(s) 36A and 36B,respectively, to produce a second alarm in correspondence with thesecond alarm signal.

[0056] Referring now to FIG. 9C, once the second alarm issues, itcontinues at TIME 2A (step 320A) until both a DISABLE #1 signal isdetected at step 322A and a DISABLE #2 signal is detected at step 322B,at which point the second alarm signal is stopped at step 324A andcontrol is returned to step 297. Essentially, processing step 320A isexecuted only if the possessor of reception portion 30A or 30B does notreturn to the vicinity of the vehicle in response to the (pre-warning)first alarm signal before TIME 2A. Once the second alarm is activated,the system 10A or 10B will disable the second alarm only if thecaregiver returns to the safety seat and both seats become unoccupied.

[0057] Although only a few exemplary embodiments of this invention havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims. In the claims, means-plus-function andstep-plus-function clauses are intended to cover the structures or actsdescribed herein as performing the recited function and not onlystructural equivalents, but also equivalent structures. Thus, although anail and a screw may not be structural equivalents in that a nailemploys a cylindrical surface to secure wooden parts together, to securewooden parts together, whereas a screw employs a helical surface, in theenvironment of fastening wooden parts, a nail and a screw may beequivalent structures.

[0058] What is claimed as new and desired to be secured by LettersPatent of the United States is:

1. A system comprising: at least one detector for monitoring thepresence of at least one object in a position; means, coupled to the atleast one detector for transmitting one of a plurality of uniquewireless signals to include a first signal when the at least one objectis in the position and a second signal when the at least one object ismoved from the position; and means, remotely located with respect to thetransmitting means, for sensing each of said first signal and saidsecond signal, the sensing means having a first timing function and asecond timing function, said first timing function being enabled whenthe sensing means senses said first signal, said first timing functiontiming to a first time interval wherein, at the completion of each saidfirst time interval, the sensing means (i) repeats said first timingfunction if said first signal is sensed, (ii) disables said first timingfunction if said second signal is sensed, and (iii) enables said secondtiming function if neither of said first signal and said second signalis sensed, said second timing function, if enabled, timing to a secondtime interval having a first time and ending at a second time that islater than said first time, the sensing means issuing a first alarmsignal at said first time if neither of said first signal and saidsecond signal is sensed thereat, the sensing means discontinuing saidfirst alarm signal if said first signal is sensed during said secondtime interval, and the sensing means issuing a second alarm signal ifsaid first signal is not sensed during said second time interval, saidsecond alarm signal continuing after said second time until said secondsignal is sensed.
 2. A system as in claim 1 wherein the at least onedetector comprises at least one switch that is an open switch wheneverthe object is not in the position.
 3. A system as in claim 2 whereinsaid at least one switch comprises at least one pressure switch.
 4. Asystem as in claim 1 wherein at least one of said first signal and saidsecond signal is an RF signal.
 5. A system as in claim 1 wherein saidfirst signal is an RF signal at a first frequency and said second signalis an RF signal at a second frequency.
 6. A system as in claim 1 whereinthe transmitting means comprises: at least one transmitter capable ofgenerating each of said first signal and said second signal; and atleast one transmitter controller coupled to the at least one detectorand the at least one transmitter for activating the at least onetransmitter to generate said first signal when the at least one detectorsenses that the at least one object is in the position and foractivating the at least one transmitter to generate said second signalwhen the at least one detector senses that the at least one object ismoved from the position.
 7. A system as in claim 6 wherein thetransmitting means further comprises audio means coupled to the at leastone transmitter controller for generating an audio output when the atleast one detector senses that the at least one object is first placedin the position and when the at least one object is first moved from theposition.
 8. A system as in claim 7 wherein the transmitting meansfurther comprises a source for supplying power to the at least onetransmitter, the at least one transmitter controller, and the audiomeans.
 9. A system as in claim 8 wherein said source is replaceable. 10.A system as in claim 1 wherein the sensing means comprises: at least onereceiver capable of receiving each of said first signal and said secondsignal; at least one receiver controller coupled to the at least onereceiver for (i) implementing said first timing function when said firstsignal is sensed by the at least one receiver, (ii) disabling said firsttiming function when said second signal is sensed by the at least onereceiver, and (iii) enabling said second timing function if neither ofsaid first signal and said second signal is sensed by the at least onereceiver after said first timing function has been enabled; and means,coupled to the at least one receiver controller, for generating at leasta first alarm in response to said first alarm signal and for generatingat least a second alarm in response to said second alarm signal.
 11. Asystem as in claim 10 wherein said first alarm is selected from thegroup consisting of audible, visible, and tactile alarms.
 12. A systemas in claim 10 wherein said second alarm is selected from the groupconsisting of audible, visible, and tactile alarms.
 13. A system as inclaim 10 wherein the sensing means further comprises a source forsupplying power to the at least one receiver, the at least one receivercontroller and the means for generating a first and second alarm.
 14. Asystem as in claim 13 wherein said source is replaceable.
 15. A systemcomprising: at least one detector for monitoring the presence of atleast one object in a position; at least one means, coupled to the atleast one detector, for transmitting one of a plurality of wirelesssignals to include a first signal when the at least one object is placedin the position, a second signal while the at least one object remainsin the position, and a third signal when the at least one object ismoved from the position; and means, remotely located with respect to theat least one transmitting means, for sensing each of said first signal,said second signal, and said third signal, the sensing means having afirst timing function and a second timing function, said first timingfunction being enabled when the sensing means senses said first signal,said first timing function timing to a first time interval wherein, atthe completion of each said first time interval, the sensing means (i)repeats said first timing function if said second signal is sensed, (ii)disables said first timing function if said third signal is sensed, and(iii) enables said second timing function if neither of said secondsignal and said third signal is sensed, said second timing function, ifenabled, timing to a second time interval having a first time and endingat a second time that is later than said first time, the sensing meansissuing a first alarm signal commencing at said first time if neither ofsaid second signal and said third signal is sensed thereat, the sensingmeans discontinuing said first alarm signal if said second signal issensed during said second time interval, and the sensing means issuing asecond alarm signal if said second signal is not sensed during saidsecond time interval, said second alarm signal continuing after saidsecond time until said third signal is sensed.
 16. A system as in claim15 wherein the at least one detector comprises at least one switch thatis an open switch whenever the object is not in the position.
 17. Asystem as in claim 16 wherein said at least one switch comprises atleast one pressure switch.
 18. A system as in claim 15 wherein at leastone of said first signal, said second signal, and said third signal isan RF signal.
 19. A system as in claim 15 wherein said first signal isan RF signal at a first frequency, said second signal is an RF signal ata second frequency, and said third signal is an RF signal at a thirdfrequency.
 20. A system as in claim 15 wherein the at least onetransmitting means comprises: at least one transmitter capable ofgenerating each of said first signal, said second signal, and said thirdsignal; and at least one transmitter controller coupled to the at leastone detector and the at least one transmitter for activating the atleast one transmitter to generate said first signal when the at leastone detector senses that the at least one object is placed in theposition, for activating the at least one transmitter to generate saidsecond signal while the at least one detector senses that the at leastone object remains in the position, and for activating the at least onetransmitter to generate said third signal when the at least one detectorsenses that the at least one object is moved from the position.
 21. Asystem as in claim 20 wherein the at least one transmitting meansfurther comprises audio means coupled to the at least one transmittercontroller for generating an audio output when the at least one detectorsenses that the at least one object is first placed in the position andwhen the object is first moved from the position.
 22. A system as inclaim 21 wherein the at least one transmitting means further comprises asource for supplying power to the at least one transmitter, the at leastone transmitter controller, and said audio means.
 23. A system as inclaim 22 wherein said source is replaceable.
 24. A system as in claim 15wherein the sensing means comprises: at least one receiver capable ofreceiving each of said first signal, said second signal, and said thirdsignal; at least one receiver controller coupled to the at least onereceiver for (i) implementing said first timing function when said firstsignal is sensed by the at least one receiver, (ii) disabling said firsttiming function when said third signal is sensed by the at least onereceiver, and (iii) enabling said second timing function if neither ofsaid second signal and said third signal is sensed by the at least onereceiver after said first timing function has been enabled; and means,coupled to the at least one receiver controller, for generating at leasta first alarm in response to said first alarm signal and for generatingat least a second alarm in response to said second alarm signal.
 25. Asystem as in claim 24 wherein said first alarm is selected from thegroup consisting of audible, visible, and tactile alarms.
 26. A systemas in claim 24 wherein said second alarm is selected from the groupconsisting of audible, visible, and tactile alarms.
 27. A system as inclaim 24 wherein the sensing means further comprises a source forsupplying power to the at least one receiver, the at least one receivercontroller, and said means for generating an alarm.
 28. A system as inclaim 27 wherein said source is replaceable.
 29. A system for alerting acaregiver that a child has been left unattended in a safety seat in avehicle, comprising: a detector for monitoring one of presence andabsence of the child in the safety seat; a transmitter maintained at thevehicle and capable of transmitting a plurality of wireless signals toinclude at least a first signal and a second signal; a receiver forpossession by the caregiver and capable of receiving each of saidplurality of wireless signals provided said receiver is within apredetermined range of said transmitter; a transmitter controllercoupled to said detector and said transmitter for monitoring saiddetector and for activating said transmitter to generate said firstsignal when said detector senses that the child is in the safety seatand for activating said transmitter to generate said second signal whensaid detector senses that the child has left the safety seat; a receivercontroller coupled to said receiver and having a first timing functionand a second timing function, said first timing function being enabledwhen said receiver is within said predetermined range and said firstsignal is sensed, said first timing function timing to a first timeinterval wherein, at the completion of each said first time interval,said receiver controller (i) repeats said first timing function if saidreceiver senses said first signal, (ii) disables said first timingfunction if said receiver senses said second signal, and (iii) enablessaid second timing function if said receiver senses neither of saidfirst signal and said second signal, said second timing function, ifenabled, timing to a second time interval having a first time and endingat a second time that is later than said first time wherein, once saidsecond timing function has been enabled, said receiver controller i)issues a first alarm signal at said first time if said receiver isbeyond said predetermined range, ii) discontinues said first alarmsignal, disables said second timing function and re-starts said firsttiming function if said receiver is brought back within saidpredetermined range during said second time interval while the child isin the safety seat, and iii) issues a second alarm signal if saidreceiver is not brought within said predetermined range during saidsecond time interval, said second alarm signal continuing after saidsecond time until said receiver is brought back within saidpredetermined range and the child is removed from the safety seat; andan audible sound producer coupled to said receiver controller forgenerating a first audio output in response to said first alarm signaland for generating a second audio output in response to said secondalarm signal.
 30. A system as in claim 29 wherein said detectorcomprises at least one pressure switch mounted on the safety seat.
 31. Asystem as in claim 29 wherein at least one of aid first signal and saidsecond signal is an RF signal.
 32. A system as in claim 29 wherein saidfirst signal is an RF signal at a first frequency and said second signalis an RF signal at a second frequency.
 33. A system as in claim 29further comprising a second audible sound producer coupled to saidtransmitter controller and maintained in the vehicle for independentlygenerating audio outputs when said detector senses that the child isfirst placed in the safety seat and that the child is first removed fromthe safety seat.
 34. A system as in claim 29 further comprising: a firstsource for supplying power to each of said transmitter and saidtransmitter controller; and a second source for supplying power to eachof said receiver, said receiver controller, and said audible soundproducer.
 35. A system as in claim 34 wherein each of said first sourceand said second source is independent of the vehicle and is replaceable.36. A system as in claim 29 wherein said first audio output and saidsecond audio output are the same.
 37. A system as in claim 29 whereinsaid first audio output and said second audio output are different. 38.A system for alerting a caregiver that a child has been left unattendedin a safety seat in a vehicle, comprising: a detector for monitoring oneof presence and absence of the child in the safety seat; a transmittermaintained at the vehicle and capable of transmitting a plurality ofwireless signals to include a first signal, a second signal and a thirdsignal; a receiver for possession by the caregiver and capable ofreceiving each of said plurality of wireless signals provided saidreceiver is within a predetermined range of said transmitter; atransmitter controller coupled to said detector and said transmitter forperiodically monitoring said detector and for activating saidtransmitter to generate said first signal only when said detector firstsenses that the child has been placed in the safety seat, for activatingsaid transmitter to generate said second signal when said detectorsenses that the child is in the car seat after a transmission of saidfirst signal, and for activating said transmitter to generate said thirdsignal when the child has left the safety seat; a receiver controllercoupled to said receiver and having a first timing function and a secondtiming function, said first timing function being enabled when saidreceiver is within said predetermined range and said second signal issensed, said first timing function timing to a first time intervalwherein, at the completion of each said first time interval, saidreceiver controller (i) repeats said first timing function if saidreceiver senses said second signal, (ii) disables said first timingfunction if said receiver senses said third signal, and (iii) enablessaid second timing function if said receiver senses neither of saidsecond signal and said third signal, said second timing function, ifenabled, timing to a second time interval having a first time and endingat a second time that is later than said first time wherein, once saidsecond timing function has been enabled, said receiver controller i)issues a first alarm signal at said first time if said receiver isbeyond said predetermined range, ii) discontinues said first alarmsignal, disables said second timing function and restarts said firsttiming function if said receiver is brought back within saidpredetermined range during said second time interval while the child isin the safety seat, and iii) issues a second alarm signal if saidreceiver is not brought within said predetermined range during saidsecond time interval, said second alarm signal continuing after saidsecond time until said receiver is brought back within saidpredetermined range and the child is removed from the safety seat; andan audible sound producer coupled to said receiver controller forgenerating a first audio output in response to said first alarm signaland for generating a second audio output in response to said secondalarm signal.
 39. A system as in claim 38 wherein said detectorcomprises at least one pressure switch mounted on the safety seat.
 40. Asystem as in claim 38 wherein at least one of said first signal and saidsecond signal is an RF signal.
 41. A system as in claim 38 wherein saidfirst signal is an RF signal at a first frequency and said second signalis an RF signal at a second frequency.
 42. A system as in claim 38further comprising a second audible sound producer coupled to saidtransmitter controller and maintained in the vehicle for independentlygenerating audio outputs when said detector senses that the child isfirst placed in the safety seat and that the child is first removed fromthe safety seat.
 43. A system as in claim 38 further comprising: a firstsource for supplying power to each of said transmitter and saidtransmitter controller; and a second source for supplying power to eachof said receiver, said receiver controller, and said audible soundproducer.
 44. A system as in claim 43 wherein each of said first sourceand said second source is independent of the vehicle and is replaceable.45. A system as in claim 38 wherein said first audio output and saidsecond audio output are the same.
 46. A system as in claim 38 whereinsaid first audio output and said second audio output are different. 47.An apparatus for alerting a caregiver that an immobile child has beenleft unattended in a safety seat, comprising: a transmitter capable oftransmitting at least one encoded wireless signal, the at least oneencoded wireless signal having a predetermined range of transmission;means, operatively coupled to the transmitter, for detecting thepresence of the child in the safety seat; means, operatively coupled tothe detecting means, for activating the transmitter to generate the atleast one encoded wireless signal when the presence of the child isdetected; means, operatively coupled to the transmitter, for tetheringthe caregiver within a predetermined distance from the immobile child,the predetermined distance corresponding to the predetermined range oftransmission of the transmitter; and means, remotely located withrespect to the transmitter, for communicating an alarm to the caregiverwhen the caregiver is beyond the predetermined distance from theimmobile child.
 48. A system as in claim 47 wherein the at least oneencoded wireless signal is an RF signal.
 49. A system as in claim 47wherein the detecting means comprises at least one switch that is anopen switch whenever the immobile child is in the safety seat.
 50. Asystem as in claim 49 wherein said at least one switch comprises atleast one pressure switch.
 51. A system as in claim 47 wherein thetethering means comprises: a receiver capable of receiving the at leastone encoded wireless signal; and a receiver controller coupled to thereceiver and having a timing function, the timing function timing to atime interval wherein, at the completion of each time interval, thereceiver controller (i) repeats the timing function when the at leastone encoded signal is sensed by the receiver and (ii) issues an alarmsignal when the at least one encoded signal is no longer sensed by thereceiver.
 52. A system as in claim 51 wherein the communicating meansfurther comprises audio means for generating at least one audio outputin response to the alarm signal.
 53. A system as in claim 52 wherein thecommunicating means further comprises a second means, operativelycoupled to the activating means, for generating an audio output when thedetecting means senses that the immobile child is first placed in thesafety seat.
 54. A system as in claim 52 further comprising a source forsupplying power to the receiver, the receiver controller, and thecommunicating means.
 55. A system as in claim 54 wherein the source isreplaceable.
 56. A system as in claim 47 further comprising a source forsupplying power to the transmitter.
 57. A system as in claim 56 whereinthe source is replaceable.
 58. A system as in claim 56 furthercomprising a second source for supplying power to the detecting meansand the activating means.
 59. A system as in claim 58 wherein the sourceand the second source are both replaceable.
 60. A method for alerting acaregiver that a child has been left unattended in a child safety seat,comprising steps for: detecting the presence of the child in the safetyseat; activating a wireless signal-sending system once the presence ofthe child is detected; tethering the caregiver with the wirelesssignal-sending system; and communicating an alarm to the tetheredcaregiver once the caregiver is beyond a predetermined distance from thechild.
 61. A method as in claim 60 further comprising a step formonitoring the child safety seat to detect the presence or absence ofthe child once the presence of the child is detected.
 62. The methodgiven in claim 61 wherein the step for monitoring the child safety seatcomprises the act of sensing the weight present in the child safetyseat.
 63. A method for alerting as given in claim 60 wherein thewireless signal-sending system comprises a transmitter and a receiverthat are operatively coupled to one another.
 64. A method for alertingas given in claim 63 wherein the step for tethering the caregivercomprises the act of maintaining the receiver in the vicinity of thecaregiver.
 65. A method for alerting as given in claim 60 wherein thestep for communicating an alarm comprises the act of sending an audiblesound to the caregiver.
 66. A method for alerting as given in claim 60wherein the step for communicating an alarm comprises the act of sendinga tactile vibration to the caregiver.
 67. A method for alerting as givenin claim 60 wherein the step for communicating an alarm comprises theact of sending a visible light to the caregiver.
 68. A method foralerting a caregiver that a child has been left unattended in a childsafety seat, comprising the acts of: sensing the presence of the childin the safety seat; sending an activating signal to a transmitter thatis operatively connected to the child safety seat, the transmitterhaving a predetermined range of transmission; transmitting a wirelesssignal to a receiver that is operatively coupled to the transmitter;tethering the caregiver by maintaining the receiver in the vicinity ofthe caregiver; and issuing an alarm once the receiver is outside thepredetermined range of the transmitter.